Multi-Input Multi-Output (MIMO) is a technique for improving data transmission/reception efficiency using multiple transmit antennas and multiple receive antennas, instead of employing one transmit antenna and one receive antenna. When a single antenna is used, a receiving side receives data through a single antenna path. However, the receiving side receives data through multiple paths when multiple antennas are used, and therefore, a data transmission rate and data transmission amount can be improved and coverage can be increased.
A single-cell MIMO operation may be divided into a Single User-MIMO (SU-MIMO) scheme in which one User Equipment (UE) receives a downlink signal in one cell and a Multi User-MIMO (MU-MIMO) scheme in which two or more UEs receive a downlink signal in one cell.
Meanwhile, much research into a Coordinated Multi-Point (CoMP) system has been carried out to improve throughput of a user located at a cell boundary by applying improved MIMO transmission in a multi-cell environment. Application of the CoMP system can reduce inter-cell interference in a multi-cell environment and can improve overall system performance.
A CoMP scheme may be classified into, for example, a Joint Processing (JP) scheme in which downlink data to be transmitted to a specific UE is shared by all of CoMP coordinated cells and a Coordinated BeamForming (CBF) scheme in which downlink data exists only in one cell. The JP scheme may further be divided into a Joint Transmission (JT) scheme in which all coordinated cells participate in signal transmission and a Cooperative Silencing (CSL) scheme in which only one cell participates in signal transmission and the other cells stop transmitting signals to reduce interference. In the CBF scheme, coordinated cells which do not transmit signals to a UE may reduce inter-cell interference by way of determining a beamforming matrix of the UE receiving signals therefrom so that the corresponding UE is subject to less interference.